A. Field Invention
This invention pertains generally to the in-circuit functionality testing of hybrid circuit components, i.e., those having both analog and digital input/output ports and more specifically to a device and procedure to provide for in-circuit measurement and testing of general purpose analog to digital converters.
B. Description of the Background
For this invention, in-circuit test or measurement refers to a printed circuit board test procedure which, through the use of various isolation techniques, performs "pin checks" or "gross functionality tests" on individual board components regardless of the specific circuit configuration or the effects of surrounding circuitry. "Pin checks" are tests specially designed to verify appropriate electrical activity on all device pins (the physical connections to the devices). "Gross functionality tests" are more comprehensive than pin checks and refer to tests designed to verify the basic function of the part in addition to simply verifying pin activity. Neither test provides full functionality testing of component specifications.
The proliferation of "hybrid" electronic components, i.e. integrated circuits incorporating both analog and digital functions in their design, has rendered standard fault detection techniques obsolete, and has created manufacturing and quality control problems for printed circuit board assemblies utilizing these devices. Central to this problem are the class of components known as converters, of which there are two basic types. The digital to analog converter (D/A) converts a digital input signal to an analog output signal, and the analog to digital converter (A/D) converts an analog input signal to a digital output signal. Neither conventional analog or digital in-circuit test techniques alone suffice as a means of performing a comprehensive in-circuit functionality test of these hybrid components. As a result, printed circuit board assemblies utilizing D/A and A/D converters have been difficult to test, due to the previously intractable problem of programmatically generating in-circuit tests for these components.